The present invention provides dispersants prepared from high polydispersity olefin polymers, which exhibit improved thickening properties especially in lubricant formulations. The invention also encompasses the intermediate acylating agents which react with amines to form such dispersants, as well as a process for preparing the same.
Dispersants are well known materials useful in a variety of applications, including especially lubricants for internal combustion engines. U.S. Pat. No. 4,234,435, Meinhardt et al., Nov. 18, 1980, discloses carboxylic acid acylating agents derived from polyalkenes and a dibasic, carboxylic reactant such as maleic or fumaric acid or certain derivatives thereof. The acylating agents can be reacted with a further reactant subject to being acylated such as polyethylene polyamines and polyols to produce derivatives useful as lubricant additives.
Polyolefins have been prepared by polymerization catalyzed with heteropolyacids. U.S. Pat. No. 5,710,225, Johnson et al., Jan. 20, 1998, discloses a method for producing polymers by polymerization of olefins, by contacting a C2-C30 olefin or derivative thereof with a heteropolyacid. The heteropolyacid catalyst can be a partially or fully exchanged with cations from the elements in groups IA, IIA and IIIA of the periodic chart, Group IB-VIIB elements and Group VIII metals, including manganese, iron, cobalt, nickel, copper, silver, zinc, boron, aluminum, bismuth, or ammonium or hydrocarbyl-substituted ammonium salt. The heteropolyacids can be used in their initial hydrated form or they can be treated (calcined) to remove some or all of the water of hydration. The calcining is preferably conducted in air at a temperature of, for instance, up to 375xc2x0 C.; temperatures much over 350xc2x0 C. do not generally provide much advantage. In the resulting polymers, the combined terminal vinylidene and xcex2-isomer content is preferably at least 30%.
U.S. Pat. No. 5,614,480, Salomon et al, Mar. 25, 1997, discloses lubricating compositions and concentrates which include carboxylic derivatives produced by reacting a substituted succinic acylating agent containing at least about 50 carbon atoms in the substituent, with certain amines. The substituent can be a polyalkene having an {overscore (M)}n value of 1300 to about 5000 and an {overscore (M)}w/{overscore (M)}n value of about 1.5 to about 4.5.
It is believed to be desirable to use highly reactive polyolefins to prepare hydrocarbyl-substituted acylating agents (e.g., anhydrides) by way of a thermal route rather than a chlorine catalyzed route. The thermal route avoids products containing chlorine. The reactivity of the polyolefin is believed to be related to the end group in the polymer with terminal olefins (terminal vinylidene) and terminal groups capable of being isomerized thereto being identified as the reactive species. The groups capable of being isomerized to the terminal vinylidene (I) group are the xcex2-isomers (II) of Table 1.
The thermal route to substituted succinic anhydrides using highly reactive PIB""s has been discussed in detail in U.S. Pat. Nos. 5,071,919, 5,137,978, 5,137,980 and 5,241,003, all issued to Ethyl Petroleum Additives, Inc.
The isomer content of a conventional (AlCl3) and high terminal vinylidene polyisobutylenes (PIB""s) are shown in Table 1. Conventional PIB has terminal vinylidene content of roughly 5%. The terminal isomer groups of conventional PIB and high vinylidene PIB are given below in Table 1 and those published in EPO 0355 895. However, in this invention polyisobutylene containing relatively high content of vinylidene and xcex2-isomers can be formed. Such materials can contain at least 30 percent terminal vinylidene (I) and xcex2-isomer (II) groups, as shown below. In preferred cases the polyisobutylene can contain at least 30 percent terminal vinylidene (I) groups, and more preferably at least 60 percent terminal vinylidene groups.
Conventional PIBs are commercially available under various tradenames including Parapol(copyright) from Exxon, Lubrizol(copyright) 3104 and 3108 from Lubrizol, Indopol(copyright) from Amoco, and Hyvis(copyright) from BP. Conventional PIBs have number average molecular weight in the range of 300-5000, but the preferred number average molecular weight is in the range of 500-2000.
The present invention provides a dispersant which is the reaction product of an amine, an alcohol, or mixtures thereof, and a hydrocarbyl-substituted acylating agent, wherein the hydrocarbyl-substituent comprises at least one polymerized olefin, the resulting polyolefin having {overscore (M)}w/{overscore (M)}n of greater than 4 or 5, preferably 6 or 7.5 to 20. The polyolefin preferably has {overscore (M)}n of at least 1500, and preferably at least 30% terminal vinylidene (I) groups.
The invention further provides a dispersant above wherein the polyolefin is prepared by contacting (a) at least one C2-C30 olefin or polymerizable derivatives thereof with (b) a catalyst comprising a partially or fully neutralized ammonium salt of a heteropolyacid, wherein said catalyst has been calcined, preferably at above 350xc2x0 C. to 500xc2x0 C.
The present invention further provides a method for preparing a dispersant, comprising the steps of reacting a hydrocarbyl-substituted acylating agent, wherein the hydrocarbyl group is a polyolefin having {overscore (M)}w/{overscore (M)}n of greater than 5, with an amine.
The present invention further provides a hydrocarbyl-substituted acylating agent, wherein the hydrocarbyl group is a polyolefin as described above.
The dispersants of the present invention include acylated amines, that is, a reaction product of one or more hydrocarbyl substituted acylating agents, particularly hydrocarbyl-substituted carboxylic acylating agents, and one or more amines characterized by the presence within its structure of at least one  greater than Nxe2x80x94H group. The acylated amines are prepared in a well-known manner by reacting normally a stoichiometric excess of amine with a hydrocarbyl-substituted carboxylic acylating agent. That is, preferably greater than 1 equivalent of amine is reacted with each equivalent of carboxylic acid of the acylating agent. In certain preferred embodiments, at least 1.2 or 1.4 equivalents, and up to 8, preferably 7, 6, or 4 equivalents of amine are reacted with each equivalent of carboxylic group of the acylating agent. In another preferred embodiment, 1.0 to 1.5 equivalents of amine are reacted with each equivalent of carboxylic acid of the acylating agent.
The acylating agents used to prepare the dispersants are hydrocarbyl-substituted acylating agents. The hydrocarbyl group is substantially a polyolefin, with polydispersity and other features as described below; generally it has a number average molecular weight of at least 600, 700, or 800, to 5000, 3000, 2500, 1600, 1300, or 1200. The hydrocarbyl group is typically derived from a polyalkene, including homopolymers and interpolymers of olefin monomers having 2 to 16, to 6, or to 4 carbon atoms, and mixtures thereof. In a preferred embodiment the polyalkene is polyisobutene. Such polyalkenes are prepared by the methods set forth in greater detail in the present invention.
Suitable olefin polymer hydrocarbyl groups, having suitable polydispersity, can be prepared by heteropolyacid catalyzed polymerization of olefins under certain conditions. Preparation of polyolefins under such conditions is also described in copending U.S. application No. 09/344,129 filed Jun. 24, 1999.
Heteropolyacids are well known materials. Such catalysts can exist as the free acid or as a salt of a heteropolyanion. Heteropolyanions are polymeric oxoanions formed by a condensation reaction of two or more different oxoanions, e.g.,
xe2x80x8312WO42xe2x88x92+HPO42xe2x88x92+23H+xe2x86x92(PW12O40)3xe2x88x92+12H2O
A variety of structures are known for these materials; they can have, for instance, the so-called Keggin structure, wherein twelve WO6 octahedra surround a central PO4 tetrahedron (in the case where phosphorus is employed). Other structures and related formulas are also known, including PW12O42, PW18O62, P2W5O23, PW9O32, PW6O24, P2W18O62, PW11O39, and P2W17O61, where P and W are taken as representative elements and the indicated structure is an ion with the appropriate charge. The central atom of the Keggin structure, which is typically phosphorus, as shown, can also be any of the Group IIIA to Group VIIA (ACS numbering) metalloids or non-transition metals, including P, As, Si, Ge, B, Al, Sb, and Te. The tungsten (W) in the above formula fills the role known as the xe2x80x9cpoly atom,xe2x80x9d which can be any of the Group VB or VIB transition metals, including W, V, Cr, Nb, Mo, or Ta. Thus suitable materials include preferably phosphomolybdates, phosphotungstates, silicomolybdates, and silicotungstates. Other combinations selected from among the above elements are also possible, including borotungstates, titanotungstates, stannotungstates, arsenomolybdates, teluromolbydates, aluminomolybdates, and phosphovanadyltungstates, the latter representing a mixed material having a formula (for the anion portion) of PW11VO40. The preferred material is a phosphotungstate, which term generally encompasses both the acid and the various salts, described below.
The heteropoly catalysts are active both as their acid form, in which the anion is associated with the corresponding number of hydrogen ions, in the fully salt form, in which the hydrogen ions have been replaced by other cations such as metal ions, or in the partially exchanged salt form, in which a portion of the hydrogen ions have been thus replaced. For more detailed information on the structures of heteropoly catalysts, attention is directed to Misono, xe2x80x9cHeterogeneous Catalysis by Heteropoly Compounds of Molybdenum and Tungsten,xe2x80x9d Catal. Rev.xe2x80x94Sci. Eng., 29(2and3), 269-321 (1987), in particular, pages 270-27 and 278-280. In the present invention, the hydrogen ions have been partially or fully replaced by ammonium, that is the catalyst is a partially or fully neutralized ammonium salt of a heteropolyacid. Moreover, the catalyst has been calcined at above 350xc2x0 C. to 500xc2x0 C.
Heteropoly acids are commercially available materials, (e.g., Aldrich Chemical Company, #22,420-0). The salts are similarly commercially available, including most notably ammonium and cesium salts. Alternatively, they can be prepared from the acid materials by neutralization with an appropriate amount of base. Heteropoly acids are generally received in a hydrated form. They can be successfully employed in this form (uncalcined) or as in the present invention, they can be treated (calcined) to remove some or all of the water of hydration, that is, to provide a dehydrated or otherwise modified species, which in the context of the present invention exhibits improved reactivity. Calcining can be conducted by simply heating the hydrated material to a suitable temperature to drive off the desired amount of water. The heating can be under ambient pressure or reduced pressure, or it can be under a flow of air or an inert gas such as nitrogen. The use of air ensures that the acid is in a high oxidation state. The flow of air can be across the surface of the catalyst, or for greater efficiency, it can be through the bulk of the catalyst. The length of time required for calcining is related to the equipment and scale, but in one broad embodiment the calcining can be conducted over the course of 5 minutes to 16 hours, more typically 30 minutes to 8 hours, and preferably 1 hour, 2 hours or even 3 hours, up to 4 hours. The upper limits of time are defined largely by the economics of the process; times in excess of about 5 hours do not generally provide much advantage.
The material which is calcined to prepare the catalysts useful for preparing polymers for use in the present invention is preferably an ammonium salt of H3PW12O40. Typical ammonium salts include (NH4)3PW12O40 and (NH4)2.5H0.5PW12O40. Each of these materials, as well as mixtures these species, are suitable. While generally the temperature of calcining will be in the range of above 350xc2x0 C. to 500xc2x0 C. and preferably 375 to 475xc2x0 C., the optimum conditions will depend to some extent on the particular ammonium salt which is selected. When the starting salt is (NH4)3PW12O40, it has been found that relatively higher temperatures are desirable for obtaining the most active catalyst. Therefore, such material is preferably calcined at 450 to 475xc2x0 C. When the starting salt is (NH4)2.5H0.5PW12O40, desirable calcining temperatures can be somewhat lower, namely, above 350 to 475xc2x0 C. and preferably above 375 to 475xc2x0 C. When the calcining temperature is too low, the catalysts may be largely or entirely inactive. For instance, when (NH4)3PW12O40 is treated at below 350xc2x0 C., it is generally found to be substantially inactive to provide the polymers of the present invention. This phenomenon is not fully understood; but, without intending to limit the generality or scope of the invention, it is believed that the high temperature calcining serves to remove a portion of the ammonia from the catalyst, thereby leading to a more active species. The time and temperature of the calcining are believed to be interrelated to some extent, so that use of temperatures in the lower ranges can be more effective when the calcining is conducted for a longer period of time, and vice versa, as will be apparent to the person skilled in the art.
The catalyst can be employed as particles of the pure salt, or it can be provided on a solid support of an inert material such as alumina, silica/alumina, an aluminophosphate, a zeolite, carbon, clay, or, preferably, silica. The source of the solid silica support can be a colloidal silica, which is subsequently precipitated during the catalyst preparation, or a silica which has already been preformed into a solid material. The catalyst can be coated onto the support by well-known catalyst impregnation techniques, e.g., by applying the catalysts as a solution, followed by drying, such as by spray drying or evaporation. If a support such as silica is employed, the ratio of the active catalyst component to the silica support will preferably be in the range of 0.5:99.5 to 50:50 by weight, preferably 3:97 to 40:60 by weight, and more preferably 10:90 to 30:70 by weight.
The temperatures used for the polymerization of olefins suitable for the present invention is preferably below 20xc2x0 C. and more preferably below 10xc2x0 C. Preferred temperature ranges are. xe2x88x9230 to 20xc2x0 C., more preferably xe2x88x9220 to 10xc2x0 C. and most preferably about xe2x88x925xc2x0 C., which is the approximate reflux temperature of isobutylene. The polymerization can be conducted in a batch apparatus or using continuous apparatus, such as a continuous stirred tank reactor or a tubular reactor, as will be apparent to those skilled in the art. The residence time of the polymerization reaction will vary with conditions including the type of reactor. Generally suitable residence times of 5 or 10 to 60 minutes, preferably 20 to 40 minutes. The polymerization can be conducted neat but is preferably conducted in the presence of a substantially inert hydrocarbon solvent or diluent, such as isobutane, pentane, hexane, octane, decane, kerosene, or Stoddard Solvent, which will normally be removed by conventional means at the conclusion of the reaction. The reaction using the catalysts of the present invention will generally provide at least a 10% conversion under these conditions, and preferably at least 20 or 25% conversion to polymer.
The preferred polymers, useful in preparing the present dispersants, are polyisobutylenes having {overscore (M)}n greater than 300. For the C4 isobutylene, this would correspond to an average degree of polymerization (dp) of about 5.3. The preferred {overscore (M)}n of polyisobutylene is at least 500 and more preferably at least 1000 or 1500, and up to 5,000, preferably in the range of 2000 to 5000. It is also generally preferred that the polymers (whether polyisobutylenes or other polyolefins) do not have an extensive low molecular weight fraction. That is, preferably they should comprise less than 10%, 5%, or 3% by weight of a fraction having a number average molecular weight of less than 350, 500, or 800 units.
Such materials are particularly useful when used in reactions to alkylate maleic anhydride and for subsequent derivatization to form the dispersants of the present invention. As well as isobutylenes, other C2-C30 olefins and derivatives thereof may be used in this invention as well as styrene and derivatives thereof, conjugated dienes such as butadiene and isoprene and non-conjugated polyenes. The reaction to produce polymers may be run with mixtures of starting olefins to form copolymers. The mole ratio of olefin substrate to catalyst in this invention ranges from 1,000:1 to 100,000 to 1.
Useful polymers produced by the process of this invention are derived from C2-C30 olefin monomers and mixtures thereof and derivatives thereof. Under this terminology, styrene and derivatives would be a C2-olefin substituted by a phenyl group.
Useful olefin monomers from which the polyolefins use in the present invention can be derived are polymerizable olefin monomers characterized by the presence of one or more unsaturated double bonds (i.e.,  greater than Cxe2x95x90C less than ); that is, they are monoolefinic monomers such as ethylene, propylene, butene-1, isobutylene, and octene-1 or polyolefinic monomers (usually diolefinic monomers) such as butadiene-1,3 and isoprene.
These olefin monomers are preferably polymerizable terminal olefins; that is, olefins characterized by the presence in their structure of the group xe2x80x94Rxe2x80x2xe2x80x94CHxe2x95x90CH2, where Rxe2x80x2 is H or a hydrocarbyl group. However, polymerizable internal olefin monomers (sometimes referred to in the patent literature as medial olefins) characterized by the presence within their structure of the group: 
can also be used to form the polyalkenes. When internal olefin monomers are employed, they normally will be employed with terminal olefins to produce polyalkenes which are interpolymers. For purposes of this invention, when a particular polymerized olefin monomer can be classified as both a terminal olefin and an internal olefin, it will be deemed to be a terminal olefin. Thus, for example, pentadiene-1,3 (i.e., piperylene) is deemed to be a terminal olefin for purposes of this invention.
While the polyalkenes used in the present invention generally are hydrocarbon polyalkenes, they can contain substituted hydrocarbon groups such as lower alkoxy, and carbonyl, provided the non-hydrocarbon moieties do not substantially interfere with the functionalization reactions of this invention. Preferably, such substituted hydrocarbon groups normally will not contribute more than 10% by weight of the total weight of the polyalkenes. Since the polyalkene can contain such non-hydrocarbon substituents, it is apparent that the olefin monomers from which the polyalkenes are made can also contain such substituents. Normally, however, as a matter of practicality and expense, the olefin monomers and the polyalkenes will be free from non-hydrocarbon groupsxe2x80x94(as used herein, the term xe2x80x9clowerxe2x80x9d when used with a chemical group such as in xe2x80x9clower alkylxe2x80x9d or xe2x80x9clower alkoxyxe2x80x9d is intended to describe groups having up to seven carbon atoms.)
Although the polyolefins useful in the invention may include aromatic groups (especially phenyl groups and lower alkyl- and/or lower alkoxy-substituted phenyl groups such as para-(tert-butyl)phenyl) and cycloaliphatic groups such as would be obtained from polymerizable cyclic olefins or cycloaliphatic substituted-polymerizable acrylic olefins, the polyalkenes usually will be free from such groups. Again, because aromatic and cycloaliphatic groups can be present, the olefin monomers from which the polyalkenes are prepared can contain aromatic and cycloaliphatic groups.
There is a general preference for polyalkenes which are derived from the group consisting of homopolymers and interpolymers of terminal hydrogen olefins of 2 to 16 carbon atoms. A more preferred class of polyalkenes are those selected from the group consisting of homopolymers and interpolymers of terminal olefins of 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms.
Specific examples of terminal and internal olefin monomers which can be used to prepare the polyalkenes of this invention include propylene; butene-1; butene-2; isobutylene; pentene-1; hexene-1; heptene-1; octene-1; nonene-1; decene-1; pentene-2; propylene-tetramer; diisobutylene; isobutylene trimer; butadiene-1,2; butadiene-1,3; pentadiene-1,2; pentadiene-1,3; isoprene; hexadiene-1,5; 2-chloro-butadiene-1,2; 2-methyl-heptene-1; 3-cyclohexyl-butene-1; 2-methyl-5-propyl-hexene-1; pentene-3; octene-4; 3,3-dimethyl-pentene-1; styrene; 2,4-dichlorostyrene; divinylbenzene; vinyl acetate; allyl alcohol; 1-methyl-vinyl acetate; ethyl vinyl ether; and methyl vinyl ketone. Of these, the hydrocarbon polymerizable monomers are preferred and of these hydrocarbon monomers, the terminal olefin monomers are particularly preferred.
Useful polymers formed in this invention include alpha-olefin homopolymers and interpolymers, and ethylene/alpha-olefin copolymers and terpolymers. Specific examples of polyalkenes include polypropylene, polybutene, ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, styrene-isobutylene copolymer, isobutylene-butadiene-1,3 copolymer, propene-isoprene copolymer, isobutylenechloroprene copolymer, isobutylene-(para-methyl)styrene copolymer, copolymer of hexene-1 with hexadiene-1,3, copolymer of octene-1, copolymer of 3,3-dimethyl-pentene-1 with hexene-1, and terpolymer of isobutylene, styrene and piperylene. More specific examples of such interpolymers include copolymer of 95% (by weight) of isobutylene with 5% (by weight) of styrene; terpolymer of 98% of isobutylene with 1% of piperylene and 1% of chloroprene; terpolymer of 95% of isobutylene with 2% of butene-1 and 3% of hexene-1; terpolymer of 60% of isobutylene with 20% of pentene-1; and 20% of octene-1; terpolymer of 90% of isobutylene with 2% of cyclohexene and 8% of propylene; and copolymer of 80% of ethylene and 20% of propylene. U.S. Pat. No. 5,334,775 describes polyolefin based polymers of many types and their monomer precursors and is herein incorporated by reference for such disclosure.
Relative amounts of end units in conventional and high vinylidene polyisobutylenes can be determined from 1H NMR spectra made using a Burker AMX 500 MHz instrument and UXNMRP software to work up the spectra. CDCl3 is used as the solvent with a sample concentration of approximately 0.10 g of sample dissolved in 1.5 g solvent with tetramethylsilane (1%) added as a reference. Band assignments in the NMR for the various isomers as parts per million (ppm) downfield shift from tetramethylsilane are: terminal vinylidene 4.68 and 4.89, xcex2-isomer 5.18, tri-substituted 5.17 and 5.35, tetra 2.88.
The molecular weight of the polymers are typically determined by GPC on a Waters(trademark) 2000 instrument run with tetrahydrofuran solvent (mobil phase). A series of 13 narrow molecular weight samples of polystyrene (m.w. 162 to 2,180,000) are preferably used as calibration standards, although known polyisobutylene can also be used as a standard. {overscore (M)}n (number average molecular weight) and {overscore (M)}w (weight average molecular weight) are determined from comparative elution volume data. Molecular weight values of the polymers produced by the method of this invention will vary according to their degree of polymerization (dp). The dp range for products of this invention typically range from 6 to 350 or even higher.
The polydispersity of the products useful in this invention as determined by the ratio of {overscore (M)}w/{overscore (M)}n have a value of at least 4 or 5 (polystyrene standard), and may have a value of up to 20 depending upon reaction conditions. At any given reaction temperature, the {overscore (M)}w/{overscore (M)}n is controlled by the chemical nature of the catalyst as well as the contact time of the olefin with the catalyst and the concentration of the olefin during the reaction. Use of the calcined ammonium catalysts of the present invention in the polymerization of isobutylene leads to polyisobutylene having a polydispersity typically greater than 4, or 5, or 6, often 7.5 to 20, more commonly 8 to 19 or 18. The polymers of suitable polydispersity are preferably prepared directly, from a single polymerization reaction, as opposed to by blending of different batches prepared from separate polymerization reactions. Of course, it is possible to blend different batches for convenience, each having suitably large polydispersity, to arrive at a composite material having a similarly large polydispersity.
It is also permitted to prepare polymeric mixtures of high polydispersity by physical admixture of samples of polymers of significantly different molecular weights, each sample individually having a relatively small value for {overscore (M)}w/{overscore (M)}n, that is, 4 or 5 or less. Such blending may produce polymeric mixtures which are polymodal (including bimodal) or otherwise non-uniform in their molecular weight distribution. Such materials may nevertheless exhibit advantages when used to prepare dispersants.
The hydrocarbyl-substituted carboxylic acylating agents of the present invention are prepared by the reaction of one or more of the above-described polyalkenes with one or more unsaturated carboxylic reagents. The unsaturated carboxylic reagents include unsaturated carboxylic acids per se and functional derivatives thereof, such as anhydrides, esters, amides, imides, salts, acyl halides, and nitrites. The unsaturated carboxylic reagents include mono-, di-, tri, or tetracarboxylic acids. Examples of useful unsaturated monobasic acids include acrylic acid, methacrylic acid, cinnamic acid, crotonic acid, and 2-phenylpropenoic acid. Polybasic unsaturated carboxylic acids include maleic acid, fumaric acid, mesaconic acid, itaconic acid, and citraconic acid; their anhydrides are preferred and maleic anhydride is particularly preferred. Reactive equivalents of such anhydrides include the above-mentioned derivative, e.g., acids, esters, half esters, amides, imides, salts, acyl halides, and nitriles, which can also serve as acylating agents. Another suitable acid is glyoxylic acid, which can be reacted with the polymer as described in U.S. Pat. No. 5,912,213. Reactive equivalents of glyoxylic acid, including esters and lactones, as well as other materials described in the foregoing U.S. patent, can also be used.
The acylating agents can be prepared by reacting one or more of the polyalkenes with, typically, a stoichiometric excess of a carboxylic acylating reagent such as maleic anhydride. Such reaction provides a substituted carboxylic acylating agent wherein the number of succinic groups, for each equivalent weight of the hydrocarbyl group, is at least 1.3, preferably at least 1.4 or 1.5, and typically up to 5, 4.5, or 3.5. That is, such acylating agents is characterized by the presence of at least 1.3 succinic groups for each equivalent weight of substituent group. For purposes of this calculation, the number of equivalent weight of substituent groups is; deemed to be the number corresponding to the quotient obtained by dividing the {overscore (M)}n, (number average molecular weight) value of the polyalkene from which the substituent is derived into the total. weight of the substituent groups present in the substituted succinic acylating agent. Thus, if a substituted succinic acylating agent is characterized by a total weight of substituent group of 40,000 and the {overscore (M)}n value for the polyalkene from which the substituent groups are derived is 2000, then that substituted succinic acylating agent is characterized by a total of 20 (40,000/2000=20) equivalent weights of substituent groups. Therefore, that particular succinic acylating agent would also be characterized by the presence within its structure of at least 26 succinic groups.
It is also possible that the acylating agent can be prepared in such a way that the number of succinic groups for each equivalent of the hydrocarbyl group is less than 1.3.
The presence of succinic groups at the above-specified levels, and the above-specified {overscore (M)}w/{overscore (M)}n ratios are believed to result in improved performance of the resulting dispersant. These features, and methods for preparing succinic acylating agents satisfying these parameters, except for the use of the materials of the high polydispersity, are described in U.S. Pat. No. 4,234,435. In particular, this patent discloses (in column 19) a process for preparing such materials by heating at a temperature of about 160xc2x0 C. to about 220xc2x0 C. a mixture comprising:
(A) Polybutene characterized by a {overscore (M)}n value of about 1700 to about 2400, in which at least 50% of the total units derived from butenes is derived from isobutene,
(B) One or more acidic reactants of the formula 
xe2x80x83wherein R and Rxe2x80x2 are each xe2x80x94OH or when taken together, R and Rxe2x80x2 are xe2x80x94Oxe2x80x94, and
(C) Chlorine.
Specific examples of preparation of such acylating agents are set forth in Examples 1 through 9 of U.S. Pat. No. 4,234,435. Similar examples can be found in U.S. Pat. Nos. 3,215,707, 3,219,666, and 3,231,587.
Other processes can be used, if desired, which do not employ chlorine, and this is often preferred if the presence of chlorine is undesirable for environmental reasons. Bromine can be used in place of chlorine; or the reactants can be heated together at 150 to 200 or 230xc2x0 C. in the absence of halogen. Preparation using a so-called xe2x80x9cthermalxe2x80x9d route is generally described in European Patent 355,895.
In the formation of the hydrocarbyl-substituted acylating agent, the conditions for the reaction of the olefin polymer with the acylating reagent such as maleic anhydride, and the relative concentrations of such components, should preferably be sufficient that a majority of the olefin polymer has reacted with at least one molecule of the acylating reagent. That is, it is preferred, for optimum performance of the dispersant, that no more than 30 percent by weight polyisobutene or other olefin polymer should remain unreacted in the resulting acylating agent and, subsequently, in the resulting dispersant. Preferably no more than 25 percent unreacted polymer should remain, and more preferably no more than 20 percent. Determination of conditions to assure a sufficient degree of reaction is within the abilities of the person skilled in the art.
Dispersants are prepared by reacting the hydrocarbyl-substituted acylating agent with an amine, an alcohol, or mixtures thereof. The amines used to prepare the dispersants can be polyamines as disclosed in U.S. Pat. No. 4,234,435 at column 21, line 4 to column 27, line 50. They may also be heterocyclic polyamines or alkylenepolyamines. Alkylenepolyamines are represented by the formula H(R1)N-(Alkylene-N(R1))nR1, where each R1 is independently hydrogen or an aliphatic group or a hydroxy-substituted aliphatic group; n is 1 to 10, 2 to 7, or 2 to 5, and the xe2x80x9cAlkylenexe2x80x9d group has 1 to 10, or 2 to 6, or 2 to 4 carbon atoms. Specific examples of such polyamines are the ethyleneamines and polyethyleneamines, such as ethylenediamine, triethylenetetramine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and mixtures thereof, including complex commercial mixtures which include cyclic condensation products. Such materials are described in detail under the heading xe2x80x9cEthylene Aminesxe2x80x9d in Kirk Othmer""s Encyclopedia of Chemical Technology, 2d Edition, Vol. 7, pages 22-37, Interscience Publishers, New York, 1965. Other amine mixtures include xe2x80x9cpolyamine bottomsxe2x80x9d which is the residue resulting from stripping of the above-described polyamine mixture. In another embodiment, the polyamine can be a condensed polyamine resulting form the condensation reaction of at least one hydroxy compound with at least one polyamine reactant containing at least one primary or secondary amino group. Such condensates are described in U.S. Pat. No. 5,230,714. Similarly, amines can be amino alcohols of any of a variety of well-known types.
Alcohols can be used in preparation of the dispersants of the present invention. Such dispersants generally then contain ester groups. Suitable alcohols can be aliphatic, cycloaliphatic, aromatic, or heterocyclic, alcohols and can contain non-hydrocarbon substituents of a type which do not interfere with the reaction of the alcohols with the acylating agent to form the ester. The alcohols can be monohydric alcohols such as methanol, ethanol, isooctanol, dodecanol, and cyclohexanol, although they are preferably polyhydric alcohols, such as alkylene polyols. Preferably, such polyhydric alcohols contain 2 to 40 and more preferably 2 to 20 carbon atoms; and 2 to 10 hydroxyl groups, more preferably 2 to 6. Polyhydric alcohols include ethylene glycols such as di-, tri- and tetraethylene glycols; propylene glycols; glycerol; sorbitol; cyclohexane diol; erythritol; and pentaerythritols, including di- and tripentaerythritol.
Commercially available polyoxyalkylene alcohol demulsifiers can also be employed as the alcohol component. Such materials include the reaction products of various organic amines, carboxylic acid amides, and quaternary ammonium salts with ethylene oxide. Some such materials are available under the names Ethoduomeen T(trademark), an ethylene oxide condensation product of an N-alkyl alkylenediamine; Ethomeen(trademark), ethylene oxide condensation products of primary fatty amines; Ethomids(trademark), ethyene oxide condensates of fatty acid amides, and Ethoquads(trademark), polyoxyethylated quaternary ammonium salts such as quaternary ammonium chlorides.
Examples of preparation of the dispersants (apart from use of the present polyolefins of high polydispersity) are found in U.S. Pat. No. 4,234,435, in particular, Examples 10 through 41 therein. For additional examples, reference may be made to U.S. Pat. Nos. 3,215,707 and 3,219,666.
The dispersants of the present invention can be further borated or treated with metallizing agents, Boration of the dispersant can be effected by well-known techniques, in particular, by reaction of the dispersant with one or more boron compounds. Suitable boron compounds include boric acid, borate esters, and alkali or mixed alkali metal and alkaline earth metal borates. These metal borates are generally a hydrated particulate metal borate and they, as well as the other borating agents, are known in the art and are available commercially. Typically the dispersant is heated with boric acid at 50-100xc2x0 C. or 100-150xc2x0 C. In a similar way, the dispersants can be metallized or treated with reactive metal containing compounds, such as zinc compounds.